Object.keys has wrong return type from 2.1

[davhdavh]

TypeScript Version: 2.1.4

Code

let test = {a:1, b:1};
let a = Object.keys(test); //currently string[]

interface ObjectConstructor2 extends ObjectConstructor {
   keys<T>(o: T): (keyof T)[];
}
let correct = (<ObjectConstructor2>Object).keys(test);

Expected behavior:
keys actually returns keys

Actual behavior:
keys returns non-specific string array

[mhegazy]

This is intentional. Types in TS are open ended. So keysof will likely be less than all properties you would get at runtime.